This invention relates to a remote manipulator of the force reflecting servomaster-slave type having seven distinct degrees of freedom, whereby it is capable of carrying out seven distinct motions. More specifically, the present manipulator uses an apparatus for translating the power input of at least two parallel drive shafts into angular or rotational output motions around two respective axes extending at right angles to each other. For this purpose, a differential drive system is used for the two motions and a further independent drive may be used for a third motion.
To the extent described in the foregoing paragraph, the present invention utilizes the same prior art as the remote manipulator disclosed in U.S. Pat. No. 3,817,403 granted on June 18, 1974 to Glachet et al. In the known manipulator it is necessary to provide at least two concentric shafts in a concentric housing arranged coaxially with a central drive shaft. All these hollow shafts and drive shafts must be provided with bearings for rotation relative to each other. Such an arrangement is cumbersome to assemble and disassemble, whereby maintenance work is not facilitated. Besides, in spite of all the concentric shafts of the prior art device this known structure requires certain power transmission elements to extend unprotected from point to point which is undesirable because it tends to cause tangling of the cable or so-called "tapes" which are used for power transmission.
U.S. Pat. No. 3,790,002 granted on Feb. 5, 1974 to Germond et al discloses a manipulator in which a drive motor block produces a continuous balancing action. However, no differential gear drive mechanism is used in this prior art device.
Various other manipulators are disclosed in my previous U.S. Pat. Nos. 3,391,804 and 3,976,206 . These previous patents also do not involve a differential gear drive system.
The above mentioned seven distinct motions include the grasping motion of the tong and three motions referred to as the wrist motions and the further motions which permit the translation of the manipulator to any point in a three dimensional space to be covered by the manipulator. The last mentioned three motions may be rectilinear or rotational, however, the most common arrangement involves three rotational motions. The present invention is specifically concerned with the last mentioned three motions which are subject to certain problems not yet satisfactorily solved by the prior art.